Is it ok for a newborn to have a lovey?

A newborn's 'lovey' is called a 'breast.' You will find it much easier, much more pleasant for both of you, and much more protective against SIDS to simply keep your baby close instead of trying to use a blanket or other mother-substitute while the child is alone in a cage. Invest in a good sling instead of stuff like blankets and 'sacks.'